body {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
font-family: Arial, sans-serif;
   
}
/* input */
.calculator {
  border: 1px solid #ccc;
  border-radius: 5px;
  padding: 20px;
  text-align: center;
  box-shadow: 2px 0 10px rgba(0, 0, 0, 0.1);
background-color: #f7d9e3;
}

.keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 20px;
  margin-top: 20px;
}
#display {
    width: 90%;
    padding: 10px;
    font-size: 30px;
    margin-bottom: 10px;
    text-align: right;
    border: 1px solid #ccc;
    border-radius: 5px;
}
button {
  padding: 15px;
  font-size: 30px;
border: none;
    cursor: pointer;
    border-radius: 100%;
    background-color: #363535;
    color: #fff;
    text-shadow: 0 1px 1px rgba(0, 0, 0, 0.5);
}
button:active {
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.5) inset;
}

button:active,
button:focus {
    outline: none;
}